In the latest years, and as a consequence of both the general structure of the vehicles and energy-sparing needs, a general tendency has been developed to create hinged-parts which are less and less voluminous, but also more and resistant because the seats must be also the place of fixations of the ends of safety-belts and, in case of a crash, the back frame must absorb by deforming a sufficient amount of energy so as to save to the passengers any violent absorption of energy and, as a consequence, to save them from being more or less injured.
The hinged-parts, which were known till now, had on the fixed side at least one hollow elongated piece enabling to maintain one of the flanges of the hinged-part onto the fixed part of the seat while the other movable hollow piece had an elongated piece which was rendered integral with the back frame and, after having included within this hollow volume, the parts which are necessary for a slow rotation of the movable flange relatively to the fixed flange, it was necessary to lock the whole unit, (1) by the central part through which the driving-shaft was guided and (2) also, on periphery of the hinged-part and generally at three or four points situated along the periphery of the hinged part. This conventional assembly permitted to obtain a certain resistance to the tearing-off of the movable flange relatively to the fixed flange when the back was practically vertical, but, as soon as the position of the back was much more inclinated, two of the support pieces of the periphery of the flanges were spaced apart from one another by an angle sometimes exceeding 180.degree., resulting in a reduction of the resistance to the tearing-off of the movable flange relatively to the fixed flange, particularly in case of lateral efforts.
The hinged-parts which are known by now also present the serious disadvantage, in order to find, as far as possible, a solution to this lack of resistance, to have their end parts treated, thus increasing the cost price and making still more difficult a junction of the treated part with the metal tubular frame or shaped sheet iron frame of the seating or the back by welding them, because this method of jointing treated parts with normal steels has never being proved to be very satisfactory.
New studies for realizing modern vehicles are obviously directed to the use of new materials (plastics materials, light alloys) in order to obtain coherent assemblies enabling by their lightness the use of engines of a small power and little consumption, but also of strong resistance to wear or in case of crash. The new studies involve studies concerning all future pieces and particularly the hinged-parts of the backs of seats. Therefore the aim of the present invention is to find a solution to all difficulties mentioned above by creating a hinged part which is compact, light and therefore pratically indestructible, and which comprises means facilitating a connection of the hinged-part with the frames of the seatings and backs, thus reducing the cost of the assemblies.
It is alternately possible, in a variant of the invention, to create a totally reversible hinged-part mechanism which can be easily blocked even by a manual control and therefore necessitating only one manufacture usable either through a motor-operated control or through a hand-operated control; thus having a much more advantageous cost.